Friends say Gibson was hospitalized last week and received four stents in his heart.
Bill Price, environmental justice coordinator for West Virginia's Sierra Club, said in the 12 years he spent working with Gibson, he rarely saw him without his bright neon t-shirt and hat broadcasting his message.
"He took simple tools and used them to engage people in the fight for justice in Appalachia. He told his story in a away that just captivated people," Price said. "After people met Larry, they never thought of things the same."
A private funeral is planned, and Larry's family has requested that those wishing to express condolences make donations to the Keeper of the Mountains Foundation, which he founded in 2004 to support mountain communities.
Larry is survived by his wife, Carol, two sons Cameron and Larry Jr. and his daughter, Victoria.
A public memorial service will be announced at a later time.
"Larry used to say, "My mother gave me birth, but the Earth gives me life', " Keating said. "He was profound."
To make a donation, visit mountainkeeper.blogspot.com.